Effects of Ga Substitution on Crystallographic and Magnetic Properties of Co Ferrites

The crystallographic and magnetic properties of gallium-substituted cobalt ferrite ($CoGa_xFe_2-xO_4$) were investigated. The new material was synthesized using conventional ceramic methods, with gallium substituted for ferrite in the range of x = 0.0 to 1.0, in steps of 0.2. X-ray diffraction and M$\ddot{o}$ssbauer spectroscopy were used to confirm the presence of crystallized particles in the $CoGa_xFe_2-xO_4$ ferrite powders. All of the samples exhibited a single phase with a spinel structure, and the lattice parameters decreased as the gallium content increased. The particle size of the samples also decreased as gallium increased. For $x{\leq}0.4$, the M$\ddot{o}$ssbauer spectra of $CoGa_xFe_2-xO_4$ could be fitted with two Zeeman sextets, which are the typical spinel ferrite spectra of $Fe³⁺$ with A- and B-sites. However, for $x{\geq}0.6$, the M$\ddot{o}$ssbauer spectra could be fitted with two Zeeman sextets and one doublet. The variation in the M$\ddot{o}$ssbauer parameters and the absorption area ratio indicated a cation distribution of $(Co_0.2-0.2xGa_xFe_0.8-0.6x)[Co_0.8+0.2xFe_1.2-0.4x]O_4$, and the magnetic behavior of the samples suggested that the increase in gallium content led to a decrease in the saturation magnetization and in the coercivity.